Recent developments in the field of vaccine production have created the need for large-scale manufacturing. Robust and high-yield processes are needed to support the world with sufficient amounts of (recombinant) vaccines to combat infectious diseases such as Polio.
Polioviruses are members of the Enterovirus genus of the family Picornaviridae. Polioviruses are small, non-enveloped viruses with capsids enclosing a single-stranded, positive sense RNA genome. There are three types of polioviruses: types 1, 2 and 3. Infections of susceptible individuals by poliovirus can result in paralytic poliomyelitis. Poliomyelitis is highly contagious. Two different polio vaccines have been developed over time, the inactivated poliovirus vaccine (IPV) of Salk and the live attenuated oral poliovirus vaccine (OPV) of Sabin. Both vaccines are safe and effective. Each has its particular advantages and disadvantages, and both have played an important role in the control of poliomyelitis. For a review about polioviruses and polio vaccines, see, e.g., Kew et al., 2005.
The culture and purification systems for producing bulk poliovirus material that can be used in a vaccine, in particular, for IPV, contribute to a large extent to the relatively high costs.
Thus, there remains a need in the art for efficient culture and purification systems for producing poliovirus for use in vaccines; in particular, there remains a need for purification processes for polioviruses with high yields.
In a typical poliovirus production process, cells are grown in specific medium and poliovirus is subsequently placed in contact with the cells to allow the virus to infect the cells and to propagate. After propagation of the poliovirus in the cells, the virus or components thereof are harvested from the cell culture.
One preferred currently used IPV manufacturing process uses anchorage-dependent, monkey-derived VERO cells that are grown on microcarriers and cultured in serum-supplemented media.
The virus produced and released in the cell culture medium can be separated from the cellular biomass by conventional methods, such as depth filtration and centrifugation. In such a case, the filtration or centrifugation is the harvesting step. The filtered harvest is typically ultra-filtrated to concentrate the viral suspension and, subsequently, the poliovirus can be purified, e.g., using gel filtration and/or ion exchange chromatography. Methods for harvesting and purifying poliovirus or viral components, and production of vaccines therefrom, have been used in the art for decades already, and thus are well known and have been amply described, for example, in Van Wezel et al., 1978; Montagnon et al., 1984; WO 2007/007344 and U.S. Pat. No. 4,525,349, all incorporated by reference herein. The resulting concentrated virus suspension can optionally be diluted, and for preparing IPV, the poliovirus therein will be inactivated, for which conventional methods can be used.
The productivities of the currently used poliovirus production processes are not sufficient to gear up IPV production volumes needed for eradicating Polio on a worldwide scale. Hence, there is a limitation in the global production capacity. In addition, the currently used production processes, due to their low productivity, have high unit operation costs because of large facility footprint and correspondingly high medium and buffer consumption, together with high (bioactive) waste production. Apart from costs associated with the vaccine manufacturing process, also product batch control and release costs scale with productivity, i.e., high productivity batches significantly drive down costs per vaccine dose.
One way of improving the yields of poliovirus production is to improve the upstream production process. Processes for production of poliovirus at high yields have been achieved by increasing the cell density of the production cultures (see, e.g., WO 2011/06823), which, however, may pose additional challenges in downstream processing. No developments for improving poliovirus purification processes have been described hitherto, either for lower or high-density cultures.
Therefore, there is a need in the industry for improved downstream processes to further increase the yields of purification processes for poliovirus.